Screening apparatus



* March 11,1958 w; R058 Q 2,826,300

SCREENING APPARATUS Filed Feb. 7. 1952 2 Sheets-Sheet 1 Mal-ch11, 195s w. ROSS 2,826,300

SCREENING APPARATUS Filed Feb. 7, 1952 2 Sheets-Sheet 2 United S 6 Claims. (Cl. 209-106) This invention relates to screening apparatus of the kind comprising screening members spaced apart in parallel relationship and over which the material moves in a direction transverse to the screening members such as is described, for example, in the specification of my prior British Letters Patent No. 376,273.

It has been found in practice that such screening apparatus is not altogether satisfactory for two reasons.

In the first place pieces of material of an awkward shape and of about the largest size which will pass through the screening aperture can become wedged between the sc-reening members causing damage to them and to the means of driving them. This can be overcome by mounting one or both of the screening members flexibly so that they can move apart from each other under a predetermined safe pressure and return after the offending piece has dropped through the danger zone but such remedy has the disadvantage that successively larger pieces of material can force the screening members apart to the limit of their flexibility at which point the ofiending piece is of a size large enough and strong enough to do very serious damage indeed to the screening members and the driving means.

In the second place, it is desirable, for the convenience of the operator to provide a means of varying the size of aperture between the screening members from time to time to suit the various materials and conditions which arise. This has previously been a lengthy operation involving, for example, moving the bearings of one of the screening members with relation to the other by means of screw jacks and has necessitated a separate drive to each member or a cumbersome and second adjustment to allow for the alteration in center length of an interscreening member chain drive. This disadvantage with respect to the drive, is to an extent also present when flexibility is required between the screening members for avoiding damage to them.

The object of the present invention is to provide an improved construction which will be free from the disadvantages above noted and the invention consists in screening apparatus of the kind referred to having the front roughened or ribbed screening member (i. e. the member furthest from the feed point) mounted so as to be easily and controllably variable in distance from the rear screening member and having an inter-screening member chain drive adapted to adjust itself automatically for any positions of the screening members relative to each other.

The invention also consists in other details and arrange ments hereinafter described or indicated.

The accompanying drawings illustrate one convenient mode of carrying out the invention.

Figure 1 is a side elevation showing one convenient form of apparatus constructed in accordance with the invention.

Figure 2 is a front elevation partly in section.

Figure 3 is a plan, and

tes Patent C Figure 4 is a sectional detail on a large scale of a part shown in Figures 1, 2 and 3.

In carrying my invention into eifect in one convenient manner I mount the bearings for the shaft of the roll a upon an arm d at each side of the machine, each arm d being rigidly fixed by a bolt 0 to the shaft b so that both arms rock together and the roll is movable away from the back roll e and still maintains its parallel relationship therewith.

One of the arms is extended and provided with a nut f which is engaged upon the screw threaded bolt g, shown in detail in Figure 4, which is adapted to be rotated by a hand-wheel h to adjust the distance between the rolls. The bolt g is resiliently mounted for longitudinal movement by being provided with a compression spring i.

The bolt g is provided with a tubular member 1 within which it may slide and upon which the nut k is screw threaded and upon which one end of the spring i rests. The load on the spring is adjustable by means of the nut k. The lower end of the spring'i rests upon an extension of the frame of the machine. There is also provided as a refinement a shock absorbing washer m of rubber or similar material upon the tubular member I to support the weight of the roll a. There is also provided a thrust bearing n to allow easy adjustment of the bolt g.

The shaft of the roll e is driven by an electric motor r through a reduction gear s and is provided with a sprocket p which carries a chain v by means of which the drive is also imparted to the sprocket p on the shaft of the roll a.

In order to allow the chain to adjust itself to different relative positions of the rolls,'there are provided the two sprockets q and q, the former being fixed as to position while the latter is movable against the action of the spring. The positioning of the sprockets q and q is such that a loop 0' is formed around the sprocket wheel p of the front roll in a position in which a line projected from the axis of pivot of roll a about the shaft b through the axis of rotation of the roll a substantially bisects this loop, and thus the roll sprocket p about the axis of b and chain loop 0' about the axis between q and q can describe two opposed arcs of circles about the axis 12 and the divergence between them when adjusting the position of the front roll is the amount represented by the curvature of the two arcs. This small divergence is allowed for by having the jockey sprocket q on the slack or non-driving side of the chain spring mounted so that the center of the loop of chain can move slightly ofi its true are and remain coincident with the sprocket p on the front roll in any position of the front roll, without imposing excessive strains on the chain.

During the screening operation a piece of material likely to jam, is caught between the rolls, and due to the rotation of the front roll, it tends to force the roll a down, pivoted about shaft b to close the aperture. The reaction to this is an upward jump of the roll about its pivot which permits the jamming piece of material to fall through the larger sized aperture or release it sufiiciently to permit of its being carried round with the surface of the roll to the oversize delivery part of the apparatus. The roll is then quickly returned to its original position by three positive forces due to (a) the weight of the roll, (b) the force of the compressed spring i, and (c) the rotation of the roll against the material flowing over it.

-It will be seen, therefore, that there is no danger of successive pieces of larger and larger size forcing the rolls further and further apart. Depending on the hardness of the material, the weight of the roll, the initial compression put into the spring i, the amount of awkward pieces of material in the feed and other factors the front roll a roller, a second roller parallelitorsaiclfi'rst roller .said second roller being ,roughened or. ribbed an axial shaftfor the first roller. drivingly connected: thereto; t bearings fixed "to the frame of the-apparatus :withimwhich thelsha fit of'the first roller is freevto rotate, an;axial shaft forthe secondroller drivingly connected thereto, bearingsdor:

each end of the secondrrolleruwithin.which thetshafttof the second roller is. free to. rotate, ,apair of lever like supportlrn'eans, one foneach endof =the.second rollcr,.

mounted upon bearings fixed "to thetframeof the apparatus for hinging about a common. axis ins. planes. at right angles;to the axis of the. fii'stlrollertthetaxis.ofirotationt of the'lever like supporttmeansvbeingttovone sidev of the planecommon to the axes ofr'the rollers,-driving-means for the shaft of'the first roller, a -sprocket wheel fast on the shaft ofth'e first roller, a sprocket wheel fast on the shaft of the second roller, a-chain between said sprocket wheels for rotating the wheels in the same direction and a resiliently mountedadjustable nut and screw means connected to the frame ofthe apparatus and at least one of the lever like support means-for adjusting the gap between the rollers and permitting limitedseparation of the rollers" against the action of the resilient mounting.

2. Screening apparatus as-claimed in claim 1 in which the said lever like support'means. are rigidly, connectedby amemberal'ong this common axisiof rotation sothat theymove together.

3. Screening apparatus as claimed "in claim 1 in which tially, horizontal and the common axis .of. rotation-of.- thelever like support means is below the second roller and outside a vertical plane through the axis of the same.

4. Screening apparatus as claimed in claim 1 in which the resiliently mounted adjustable nut and screw means is connected to the lever like support means on the opposite side of the common axi's ofrotation of the latter to the bearings forthe second rol1'er;,the resilient mounting comprising a helical spring concentric with. the screw which urges tli'e-second rollertowardsthefirst roller.

5. Screening apparatus assclaimed-intclaim"1 in: which the chain is supported between the said sprockets by a pairi ofijockey 'sprockets to "forma substantially parallel sided loop around. the sprocket of the. second roller, the general direction ofsaid'loop coinciding with a plane passing through the common axis of rotation of the lever like support members and the axis of the second roller.

6'1; Screening;apparatus-:as= claim'ed -in clai-n'r-S in" which the jockey sprocket on. thernon dr-iv-i'ng siderof the secondrolleris; spring mounted so :that sli'ghtvariations in chain shape: are! possiblerwithout:overstraining the chain;

References Cited '-'in fthe file fof this patent UNITED STATES PATENTS 484;2'58" swan; -t Oct. 11, 1892 751,672 McCormick -7 Feb. 9, 1904 1,999,574- Paxton Apr. 30, 1935 2,082302 Ross June 1, 1937 2,437,733 Fiilchel" Mar. 176, 1948-v 2 4661089 Each ..-'Apr. 5, 1949 2,431,201 Collier Sept. 6, 1949 25601837 Alciatfet all July 17, 1951 2,612,321' sidwell et a1. Sept. 30, 1952 

